1. Field of the Invention
The present invention relates to a method and apparatus for continuously manufacturing a fastener stringer in which a plurality of engaging elements are implanted at a predetermined interval on one side edge of a fastener tape.
2. Description of the Related Art
As disclosed in, for example, Japanese Patent Application Publication No. 59-51813, this kind of fastener stringer is usually obtained as follows. That is, a long metallic wire rod having a circular section is molded so as to have a substantially Y-like shape in its lateral section through a plurality of mill rolls and cut successively with a predetermined thickness by a cutting punch and a cutting die so as to obtain individual engaging elements. An engaging head is formed into a mountain-like shape by a forming punch and a forming die so as to obtain an engaging element comprising an engaging head and attaching legs (hereinafter referred to as a “wire rod engaging element”). Subsequently, the engaging elements are implanted successively to a fastener tape by pressurizing the attaching legs with a pressurizing hammer.
According to the method for continuously manufacturing the fastener stringer, the engaging elements are produced from one continuous engaging element metallic wire rod having a circular section and the engaging elements are implanted successively to the fastener tape, thereby making it possible to manufacture the fastener stringer securing an excellent productivity without any production loss. However, because the individual engaging elements are produced by cutting a long wire rod with a predetermined thickness by a cutting punch, burr is always generated on its cutting end, so that it is difficult to obtain a smooth curved surface.
To eliminate such an inconvenience, for example, the inventor has already proposed an engaging element forming method as disclosed in Japanese Patent Application Laid-Open No. 8-56714. In this engaging element forming method, a chamfering face for chamfering an outside ridge portion on a periphery of a leg is formed on a pressurizing face of a pressurizing hammer. Then, chamfering is carried out by rolling the ridge portion on an outer periphery from the leg of the engaging element to a part of the engaging head at the same time when the engaging element is pressurized with the pressurizing hammer.
In the meantime, in this kind of the fastener stringer continuous manufacturing apparatus, after a main ram equipped with a cutting die and a forming die retracts and a metallic wire rod is cut, the main ram continues to retract further, so that an engaging element cut by a cutting punch provided on the frame is pushed forward and automatically moved to a position for forming a head of the engaging element into a mountain-like shape by a forming punch. A pressurizing hammer supports attaching legs of the engaging element carried to the forming die from either side of the engaging element. Immediately thereafter, the forming punch descends so as to form the head of the engaging element into a mountain-like shape. After the forming into the mountain-like shape is ended, the main ram advances forward so as to move the engaging element on the forming die forward to a pressurizing position. At this time, the pressurizing hammer moves obliquely forward together and starts its pressurizing operation, so that a crotch portion between the attaching legs of the engaging element is pressed against the edge of an engaging element implantation portion of the fastener tape, and at the same time, the pressurization of the attaching legs is completed.
Substantially at the same time when the pressurizing hammer is actuated to pressurize the engaging element to the fastener tape, feeding of the fastener tape is started, and immediately thereafter, the main ram begins to retract again. The above-described motion of the pressurizing hammer aims at pressurizing the attaching legs of the engaging element gradually from the engaging head toward the leg tips and securing a required stroke length. Thus, the pressurizing hammer is formed in a parallelogram, and a pressurizing face at its inclined short side is introduced to a sliding groove of the pressurizing hammer which traverses obliquely a substantially half portion of an auxiliary ram by a pressing force of the actuating face of an actuating lever swung by a cam face formed on the side face of the auxiliary ram interlocking with the motion of the main ram. Consequently, the pressurizing hammer reciprocates linearly and obliquely forward over the substantially half portion of the ram. Here, an elastic force which presses the actuating face of the actuating lever is always applied to the pressurizing hammer. By using this elastic force, the pressurizing hammer is retracted quickly by the retracting action of the auxiliary ram and the elastic force regardless of its large stroke length, thereby avoiding an interference with the cutting punch securely.
However, if it is intended to chamfer at the same time when the attaching legs of the engaging element are pressurized with the pressurizing hammer as described in the above-mentioned Japanese Patent Application Laid-Open No. 8-56714, not only a chamfered portion becomes longer than a conventional stroke length but also a load on an operated pressurizing hammer increases by an amount corresponding to the chamfered portion. Thus, it is necessary to further sharpen an inclination angle of a front end of the pressurizing hammer and also to increase a swing angle of the actuating lever and further an inclination of the aforementioned cam. This unavoidably leads to an enhancement of the strength of the actuating lever and an increase in size of the apparatus.